Generally, removing apparatus for alien material used in chemical factories and plastic powder manufacturing factories serve to remove metallic alien materials contained in raw materials in order to achieve an improvement in the quality of those raw materials.
An example of a metal separation device was disclosed in U.S. Pat. No. 5,188,239 of Stowe et al. This metal separation device will be described with reference to FIG. 6.
As shown in FIG. 6, the metal separation device includes a housing 12, into which a raw material is introduced, and a bracket 30 mounted in the housing 12. The bracket 30 includes a base plate 36, leg members 40 extending from the base plate 36, and a face plate 26 coupled to the leg members 40 in such a fashion that it is integral with those leg members 40. The base plate 36 and leg members 40 are disposed in the interior of the housing 12 whereas the face plate 26 is coupled to one side wall of the housing 12. The base plate 36 and faceplate 26 are provided with holes 38 and 28, respectively. Cylindrical magnets 23 are separable inserted into the holes 38 and 28 at respective one-side ends thereof. A drawer plate 25 is coupled to the other-side ends of the magnets 23. A handle 58 is provided at the drawer plate 25.
As a raw material passes through the housing 12 under the condition in which the magnets 23 are inserted in the holes 28 and 38 of the face plate 26 and base plate 36 included in the bracket 30 fitted in the housing 12, metallic alien materials contained in the raw material are attached to outer surfaces of the magnets 23. When the operator pulls the handle 58 to draw the magnets 23 from the housing 12, the magnets 23 slide with respect to the holes 28 of the faceplate 26. Since the outer surface of each magnet 23 is in contact with the peripheral surface of an associated one of the holes 28, the metallic alien materials attached to the outer surfaces of the magnets are wiped by the peripheral surfaces of the holes 28. Thus, the metallic alien materials are removed from the outer surfaces of the magnets 23.
However, the metal separation device of Stowe et al. has the following drawbacks.
First, fine metallic alien materials attached to the magnets 23 are left without being completely removed. For this reason, a separate manual process using an adhesive tape or the like should be conducted in order to remove such fine metallic alien materials.
In addition, a lot of time is taken for the manual process, thereby resulting in degradation in productivity.
After the magnets 23 are separated from the bracket 30, they should be inserted again into the bracket 30. However, it is difficult to insert the magnets 23 into the holes 28 and 38 of the bracket 30 by virtue of the magnetic force of the magnets 23. In other words, the free end of each magnet 23 cannot be easily inserted into the hole 28 or 38 of the bracket 30 because the fundamental magnet characteristics, that is, an attraction exhibited between magnets having the same polarity and a repulsion exhibited between magnets having different polarities.